Method of continuously producing a phosphorus sulfide



June 4, 1957 R, B HUDSON f 2,794,705

METHOD lQF CONTINUOUSLY P RODUCING A PHOSPHORUS SULFIDE ,Filed July 23,1954 INVENT ATTORNEY United States Patent O METHOD F CNTINUUSLYPRODUCING A PHOSPHORUS SULFIDE Robert B. Hudson, Trenton, Mich.,assigner to Monsanto Chemical Company, St. Louis, Mo., a corporation ofDelaware Application July 23, 1954, Serial No. 445,329

6 Claims. (Cl. 23-206) This invention relates to phosphorus suldes andto an improved method of producing same.

Heretofore, phosphorus suldes have been prepared continuously byintroducing phosphorus and sulfur with agitation into a molten heel ofphosphorus sulde and reacting these materials in the proportionscalculated to yield the desired product. In carrying out this reaction,the exothermic heat is absorbed by the molten heel of phosphorus suldeand thereby transferred to a suitable heat exchanging material orsurface. The product of this reaction is withdrawn continuously from thereaction zone, aked on chill rolls and then converted into a powder bygrinding in a hammer mill or equivalent .pulverizing device. This methodprovides a means of producing phosphorus sulfldes continuously but issubject to certain disadvantages which render the method and productcommercially unattractive.

For example, in this method the high heat ofL reaction, high meltingtemperature and high viscosity of phosphorus suliides combine to presenta very diicult heat transfer problem and consequently a reaction potwith a large heat transfer area is required. Moreover, vigorousmechanical agitation is essential to increase the heat transfercoeicient and to assure efficient mixing and this iuvolves the use ofmechanical agitators and seals with their attendant costs. In addition,darkly colored products invariably result from this method as a resultof the accumulation yof impurities including those derived from the rawmaterials and metal equipment and'while the color of these products maybe improved by distillation, such treatment involves additional heat andequipment, all of which add substantially to the overall cost ofmanufacturing these products. Furthermore, Variation from predeterminedfeed rates in this method yields products of heterogeneous compositiondue to the inclusion of impurities such as excess phosphorus, sulfur orphosphorus suldes other than the one desired.

Therefore, it is the primary object of the instant invention to providea continuous method of producing phosphorus suliides of uniformcomposition, which overcomes the disadvantages outlined above. .Anotherobject is to provide a continuous method of producing phosphorus suldeswhich is more economically and commercially feasible than the abovedescribed method. Other objects and advantages of the present inventionwill become apparent to those skilled in the art as the descriptionproceeds.

I have developed a relatively simple method of manufacturing phosphorussuldes continuously, which represents a substantial advance in the artover the method described earlier herein. In accordance with thismethod, phosphorus and sulfur are introduced continuously into a heel ofboiling phosphorus sulfide contained in a combined reactor and stillwherein the exothermic heat of the phosphorus-sulfur reaction eifectscontinuous distillation of the resulting reaction product. This hotdistillate is conveyed continuously to a hot condenser where thephosphorus sulfide vapor is condensed substantially com- 2,794,705Patented June 4, 1957 rice A pletely while the uncondensed gases andphosphorus sultide vapors are vented to the atmosphere. The condensedliquid phosphorus sulfide is cooled further and fed continuously onto achill roll which solidities and breaks up the product into akescontinuously. If desired, the phosphorus sulde from the combined reactorand still may be cooled in the condenser to a safe operating temperatureand fed continuously yonto the chill roll. After leaving the chill roll,the akes are ground continuously into a powder by means of a hammer millor another equivalent pulverizing device.

For a more complete understandingjof the improved method of makingphosphorus suldes, reference is made to the accompanying ow sheet whichconstitutes part of the instant specification. Y

Reference characters l and V2 represent phosphorus and sulfur feed tanksfrom which these reactants are continuously fed by nitrogen pressure vialines 3 and 4, respectively, into a heel of phosphorus sulfide containedin a combined reactor and still 5, the nitrogen used for this purposebeing introduced into tanks 1 and 2 by way of lines 6 and 7,respectively.

The combined reactor and still 5 includes a still pot and incommunication therewith a packed column containing porcelain Berlsaddles, .Pyrex glass rings and wool or equivalent materials. Thiscombined reactor Vand still 5 is provided with an outlet line 8 fordischarging still bottoms therefrom and a discharge line 9 for conveyingthe distilled phosphorus sulfide vapors from the packed column section(not shown) of the still to a hot condenser 10.

The. condenser 10 is provided with a jacket 11 having a inlet line 12for introducing a heat exchanging medium at a temperature of about 300C. and an outlet line 13 for discharging the heat vexchanging medium ata temperature of about 305 C. from the jacket. The condenser is alsoequipped with a vent line 14 for discharging the inert incondensible gasand traces of phosphorus sulfide from the system, a take-off line 15 forconducting the condensed liquid phosphorus sulfide to a cooler 16; and aline 16 for returning reilux to the combined reactor and still 5.

The cooler 16 is provided with a jacket 17 having an inlet line 18 forintroducing a heat exchanging medium at a temperature of about 300 C.and an outlet line 19 for conducting the heat exchanging medium at atemperature `of about 305 C. from the jacket 17. In addition, the cooler16 is equipped with a discharge line 20 for conveying the cooledphosphorus sulfide into an enclosed chill wheel 21.

The chill wheel 21 is cooled by means of Water or another suitablemedium introduced by line 22 and discharged therefrom by line 23; inaddition, in order to avoid combustion of the phosphorus sulde beingflaked, it is blanketed by means of an inert gas `such as nitrogen orcarbon dioxide which is introduced by line 24 into the enclosuretherefor (not shown) and discharged therefrom by means of line 25. Thischill wheel 21 is provided with an outlet line 26 through which the akedphosphorus sulfide is conveyed to a grinding mill 27 where the akes areground to a finely divided state.

The grinding mill 27 is purged by means of an inert gas such as nitrogenor carbon dioxide, etc. which-enters the mill by line 28 and leaves byline 29,the purging being done as a precautionary measure to avoidcombustion of the phosphorus sulfide. This grinding mill is providedwith a line 30 for conveying fines to a 'dust collector 31 from which aportion of the inert purging gas is vented into the atmosphere by line32. The grinding mill 27 is further provided with a line`33 forconveying the iinal product to the packaging plant 34.

.The following.example-illustrates the method of carrying out theinstant invention employing the system illustrated in the accompanyingdrawing.

, Y n. l Example Y d p The combined reactor and still 5 was chargedlwith about 150 lbs. lof phosphorus pentasulde and then heated toatemperature of about 515 C. so as to provide a fluid heel or reactionmedium for the phosphorus-sulfur reaction.

Liquid phosphorus and liquid sulfur, both under nitrogen pressure, wereintroduced continuously into the above heel of phosphorus pentasulde atflow rates corresponding to 31 lbs. and 80 lbs., per hour, respectively,said iiow rates being suthcient to maintain a reaction temperature ofabout 515 C. The exothermic heat produced as a result ofthe reactionbetween the phosphorus and sulfur caused theresulting phosphoruspentasulfide to distill continuously from the combined reactor and still5. This distillate including the inert gas was conveyed continuously Vtothe condenser where the phosphorus pentasulde was cooled to atemperature of about 500 C. and condensed While the inert gas and smallamounts of phosphorus pentasuliide were vented by line 14 into theatmosphere. The condensed liquid phosphorus pentasulde was conductedcontinuously to the cooler 16 and cooled down to a temperature of about300 C.-350 C. whereupon it vlas fed to the chill wheel 21 and convertedcontinuously into flakes. These akes were conveyed continuously to thegrinding mill and converted into a powder at a rate of about 100 lbs.per hour.

The phosphorus pentasultde thus obtained had a melting point of about280 C. and a greyish yellow color as vcontrasted to the substantiallyjet black color of the phosphorus pentasulde produced Vby the lowtemperature method described earlier herein.

In like'rmanner phosphorusheptasulde and phosphorus sesquisulide havingan improved color can be produced -in a continuous manner bycontinuously feeding the reactants in the proportions required to yieldthese products Vand by operating at a temperatureequivalent to theboiling points of the heptasulde and sesquisulde, respectively, attheoperating pressure.

In theproduction of phosphoruspentasulfide in accordance with theinstant invention, phosphorus and sulfur are continuously fed to acombined reaction and distillation zone where they are reacted together,in a heel of the product to be formed, and at a temperature at leastequivalent to theboiling point of the reaction product at the operatingpressure. When operating at atmospheric pressure, the reactiontemperature used in the formation of phosphorus pentasulde should fallsubstantially in the range of about 505 C. to 525 C., whereas in theproduction of phosphorus sesquisulde and phosphorus heptasulde, thereaction temperature should fall within the ranges of from about 400 C.to about 420 C. and from about 520 C. to about 535 C., respectively.

The reactants are introduced continuously into the heel of phosphorussullide at a rate producing a reaction temperature at least equivalentto the boiling point of the phosphorus sulfide, thus insuring continuousdistillation of this product substantially as rapidly as it is formed.The excess heat developed as a result of this reaction may be absorbedby returning a portion of the condensed phosphorus sulfide to thecombined reaction and distillation zone.

The product leaving the combined lreaction and distillation zone iscooled to condense the phosphorus sulde, the temperature used varyingwith the particular phosphorus sulfide being produced. In the case ofphosphorus pentasuliide, the product from the combined reaction anddistillation zone is cooled to a temperature of about 500 C. or to alower temperature above its solidiication point to effect substantiallycomplete condensation of the phosphorus pentasulde.

The condensed phosphorus pentasulde at a temperature of about 500 C. owsinto a cooler where itis cooled to about 300 to 350 C. However, thistemperature is not fixed since it varies with the phosphorus suliidebeing produced, the only limitation being that the liquid phosphorussuliide should not be cooled to a temperature preventing free iiowthereof onto the chill wheel. This cooling step may be omitted if theproduct is cooled to a safe operating temperature in the condensationzone.

The liquid phosphorus sullide is discharged continuously from thecondenser or cooler onto a chill wheel and converted into tiakes whichare introduced continuously into a grinding mill where they are groundto a finely divided state.

The aking and grinding operations are preferably carried out in thepresence of a dry inert atmosphere, but the invention is by no meansrestricted thereto since this is merely a desirable precautionarymeasure designed to prevent decomposition of the product by air andmoisture.

The products of the instant invention are suitable for use in organicsynthesis and in a number of commercial applications such as in themanufacture of extreme pressure lubricants, match compositions andvulcanized rubber.

K What I claim is:

l. The method of continuously producing a phosphorus sulde, whichcomprises continuously introducing liquid :phosphorus and liquid sulfurinto a boiling mass consisting of said phosphorus sulde and therebyeffecting a continuous reaction between said phosphorus and said sulfurand continuous distillation of said reaction product, said reactantsbeing introduced continuously into said boiling mass in substantiallythe proportions calculated to yield said phosphorus sulfide and at arate maintaining said mass in a boiling condition.

2.Y The method of continuously producing a phosphorus sulfideselectedfrom the group consisting of phosphorus pentasuliide, phosphorusheptasuliide and phosphorus sesquisulde, which comprises continuouslyintroducing liquid phosphorus and liquid sulfur into a boiling massconsisting of said phosphorus sulfide and thereby etiecting a continuousreaction between said phosphorus and said sulfurV and continuousdistillation of said reaction product, said reactants being introducedcontinuously into said boiling mass in substantially the proportionscalculated to yield said phosphorus sulfide and at a rate maintainingsaid mass in a boiling condition.

3. The method of continuously producing a phosphorus sulde selected fromthe group consisting'of phosphorus pentasulde, phosphorus heptasuliideand phosphorus sesquisuliide, which comprises continuously introducingliquid phosphorusand liquid sulfur into a boiling mass consisting ofsaid phosphorus suliide and thereby effecting a continuous reactionbetween said phosphorus and said sulfur and continuous `distillation ofsaid reaction products, and continuously recovering said reactionproduct, said reactants being introduced continuously into said boilingmass in substantially the proportions calculated to yield saidphosphorus suliide and at a rate maintaining said mass ina boilingcondition.

4. The method of continuously producing a phosphorus sulfide selectedfrom the group consisting of phosphorus pentasullide, phosphorusheptasulfde and phosphorus sesquisuliide, which comprises continuouslyintroducing liquid phosphorus and liquid sulfur into a boiling massconsisting of said phosphorus sulfide and thereby eiiecting a continuousreaction between said phosphorus and said sulfur and continuousdistillation of said reaction product, continuously recovering saidreaction product, continuously aking said recovered reaction product andcontinuously grinding it into a .iinely `divided state, said reactantsbeing introduced continuously into said boiling mass insubstantiallyjthe proportions calculated to yield said phosphorussuliide and at ra rate maintaining said mass in aboiling condition. v

5.Y The method of continuously producing phosphorus pentasulde, whichcomprises continuously introducing liquid phosphorus and liquid sulfurinto a boiling mass consisting of said phosphorus pentasulde and therebyeffecting a continuous reaction between said phosphorus and sulfur andcontinuous distillation of the phosphorus pentasulde product, saidreactants being introduced continuously into said boiling mass insubstantially the atomic ratio of two parts of phosphorus to five partsof sulfur and at a rate maintaining said mass in a boiling condition.

6. The method of continuously producing phosphorus pentasuliide, whichcomprises continuously introducing liquid phosphorus and liquid sulfurinto a boiling mass consisting of said phosphorus pentasulde and therebyeiecting a continuous reaction between said phosphorus and sulfur andcontinuous distillation of the phosphorus pentasuliide product, saidreactants being introduced continuously into said boiling mass insubstantially the atomic ratio of two parts of phosphorus to ve parts ofsulfur and at a rate maintaining the reaction temperature within theboiling range of about 505 C. to about 525 C. at about atmosphericpressure.

References Cited in the file of this patent UNTED STATES PATENTS2,569,128 Jones Sept. 25, 1951

1. THE METHOD OF CONTINUOUSLY PRODUCING A PHOSPHORUS SULFIDE, WHICHCOMPRISES CONTINUOUSLY INTRODUCING LIQUID PHOSPHORUS AND LIQUID SULFURINTO A BOILING MASS CONSISTING OF SAID PHOSPHORUS SULFIDE AND THEREBYEFFECTING A CONTINUOUS REACTION BETWEEN SAID PHOSPHORUS AND SAID SULFURAND CONTINUOUS DISTILLATION OF SAID REACTION PRODUCT, SAID REACTANTSBEING INTRODUCED CONTINUOUSLY INTO SAID BOILING